More than 300,000 Americans die each year when the heart suddenly stops pumping blood, triggered by an electrical disturbance in the heart.

Researchers at The Johns Hopkins University School of Medicine and its Donald W. Reynolds Cardiovascular Clinical Research Center received $12.6 million in additional funding from its namesake, the Las Vegas-based Donald W. Reynolds Foundation, to continue seeking the causes of sudden cardiac death.

“Sudden cardiac death often occurs in people who appear healthy,” said Dr. Eduardo Marbán, Hopkins’ chief of cardiology and director of the Reynolds Center. “So it has been a major medical challenge to identify who is most at risk for this tragic outcome.”